Centralized traffic controlling system for railroads



Juhe 1, 1937; T. J. JUDGE ET AL CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Original Filed Oct. 28, 1932 8 Sheets-Sheet 1 um m Lopn INVENTORS TJ'J'udge 4 CSBushneH,

June 1, 1937. T. 'J. JUDGE ET AL I CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Original Filed Oct. 28, 1932 8 Sheets-Sheet 3 J1me 1937- T. J. JUDGE ET AL CEN'EFRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS 8 Sheets-Sheet 4 Original Filed Oct. 28, 1932 INVENTORS Y E .N MR m E O M d R U I J E JY m TB I June 1, 1937. T. J. JUDGE ET AL CENTRALIZED TRAFFIC CONTROLLjING SYSTEM FOR RAILROADS 8 Sheets-Sheet 5 hnel I,

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INVENTORS r 3 5 mm F m m 00m IQME :2 50 2 8 E I moo m3 m2 Um+ 22C 5 us TORN-EY June 1', 1937. T. J. JUDG E ET AL 2,082,544

CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Original Filed Oct. 28, 1932 8 Sheets-Sheet 6 m M M e qCsBushr lel l,

m 0 T 0 m T V 9. M Nd R I E. Y TB June 1, 1937. T, J JUDGE ET AL 2,082,544

CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Original Filed Oct. 28, 1932 8 Sheets-Sheet 8 TYPICAL CODE TABLE First First Jecond Second Third Energized Deeneryizd EnergizedDeenergized Energized Period Period Period Period Period Station 1 Selecting 2 Codes 5 4 Posatlve Impulse 5 Negative Impulse 6 v Code No.8 is not 7 assi n ed to any Field 8 Station 1 2 i itatlon a Registering 4 C des 5 6 7 5 9 Closed IndicationlO Circuit 11 0P Indieation 12 Circuit 15 Code No.16. is not 14 assignd to any 15 Field Station 16 INVENTORS g' JfJudge '"v/CS. ushnelL Patented June 1, 1937 UNITED STATES CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR BAILROADS Thomas J. Judge and Charles ester, N. Y., assignors to General S. Bushnell, Roch- Railway Signal Company, Rochester, N. Y.

Application October 28, 1932, Serial No. 640,062 Renewed March 27, 1936 23 Claims.

This invention relates to centralized traffic controlling systems for governing traffic on railroads, and more particularly pertains to the communication part of such systems.

In a centralized traffic controlling system of the type contemplated by this invention, the switches and signals at various points along a railroad are placed under the control of an operator in a central control oflice, in such a way that the operator may at will change the position of the switches subject to automatic approach and detector locking circuits which prevent unsafe operation of any switch, and in such a way that the operator may at will hold at stop any of the signals or allow them to clear dependent upon the position of the associated switches and the location of trains within certain track sections, so that the signals will indicate proceed only when it is safe for the passage of traflic. Also, the system provides means whereby indications are displayed in the control ofiice to inform the operator of the presence or absence of trains on various track sections throughout the territory under his supervision, and to show the operated positions and conditions of the various switches, signals and other traffic controlling devices located in the territory.

The switches and signals of a railroad system are not usually evenly distributed throughout the system, but some are located near or adjacent to each other while others are at considerable distances. That apparatus, located within a limited area determined by the convenience and economy with which the apparatus may be interconnected by direct control wires, is conveniently termed a field station. A code type selective communication system is then provided to interconnect the control office with the several outlying field stations for the transmission of controls and indications to and from these field stations.

This code selective type communication system requires only a small number of line wires to establish communication between the control ofiice and a large number of field stations with means providing for the transmission of a large number of controls and indications for each of the field stations. The system is of the two circuit type having a control line circuit and an indication line circuit, which circuits are made up by the provision of at least three line wires, one control line wire, one indication line wire and a common return line wire. In

the illustrations, however, the control line is provided with an individual return line, and similarly, the indication line is provided with an individual return line.

Communication is established between the control office and the several field stations by the transmission of suitable codes, which cause the selector type apparatus at each location to operate step-by-step through cycles of operation. The system embodying the present invention, is of the station selective coded duplex type, wherein controls and/or indications may be transmitted during any particular operating cycle of the system.

For the transmission of controls, a series of impulses of selected polarities is placed upon the control line circuit. The apparatus at the control ofice and at each field station is operated through a cycle of operation (with exceptions hereinafter described) for each series, irrespective of the character of the impulses of the series, while the character of the impulses of each series determines the particular station selected for that cycle and the controls transmitted to that selected station. a

For the transmission of indications, a series of impulses is placed upon the indication line circuit, which impulses set up distinctive conditions by reason of their presence or absence on the steps of each cycle, as marked off by impulses placed upon the control line circuit.

With such an arrangement, whenever-a cycle of operation occurs for the transmission of indications alone, then the series of impulses placed upon the control line circuit for causing the step-by-step operation must be of such a character as not to select any field station, but

to merely cause the step-by-step operation at that field station then transmitting its indioations. Similarly, whenever a cycle of operation occurs for the transmission of controls alone, then there are no impulses placed upon the indication line circuit, thereby setting up distinctive conditions which form a code, and this code is not employed by any field station, so as to prevent the false registration of a station when it is not transmitting indications.

One feature of the present invention resides in the manner in which stations are selected for the reception of controls, and the manner in which stations are registered in the control ofiice for the transmission of indications.

Another feature of the present invention more particularly resides in the manner in which impulses are placed upon the indication line circuit so as to increase the speed of operation in a system which substantially doubles the capacity of the indication line circuit over the capacity of the control line circuit. For example, one energization and one deenergization of the control line circuit has usually been designated as comprising a single step. In previous systems, the field stations have been arranged so that the indications were transmitted by the pulsing of the indication line circuit once for each step. In accordance with the present invention, the indication line circuit is preconditioned and impulsed twice during each step, namely, once during the energized period of the control line circuit and also once during the deenergized period of the control line circuit.

This double capacity pulsation of the indication line circuit is accomplished in a novel manner by the branching of the indication line circuit into two branches at the control oflice and at each field station, with the corresponding branches at the several locations connected in series at any one time by the use of the relays responsive to the presence or absence of impulses on the control line circuit. In this connection, special means is provided for preconditioning the respective branches of the indication line circuit at the field stations so as to more quickly transmit such conditions to the corresponding branches in the control ofiice. This is accomplished by the elimination of certain operations previously required at a field station between the change from one condition to the other on the control line circuit.

A system arranged in this manner for the double capacity transmission of impulses over theindication line circuit is particularly desirable for centralized trafiic controlling systems, as the circumstances of practice have taught that the desirable number of indications to give the best facility in train operation is now considered to be substantially double the number of controls required for the positioning of the traffic governing devices throughout the controlled territory.

Another feature of the present invention resides in the manner in which the selector type apparatus at the several field stations is so controlled that it ceases to respond to impulses impressed on the control line circuit whenever the respective field station fails to be selected. This functioning of the system of the present invention includes not only the stopping of the usual step-by-step means but also the stopping of the operations of all other controlling relays except the relay included in the control line circuit. This feature of the present invention is particularly desirable where relays are employed in that all relay operations are discontinued, thereby eliminating considerable unnecessary wear of their operating parts.

A further feature of the invention resides in the improved arrangement of code determining relays in the control office for setting up the interlock between the control levers for the several stations to thereby allow the transmission of but a single code callfor any one particular cycle of operation. In connection with this code determining bank, an improved polarity selecting means is provided whereby the failure of a circuit or a short between circuits results in the stopping of the cycle of operation rather than the erroneous transmission of impulses. This is accomplished by the provision of two neutral polarity selecting relays, one for positive impulses and one for negative impulses.

These characteristic features of the present invention, thus briefly stated, will be explained more in detail in the following description of one embodiment of the invention; and various other characteristic features, functions and advantages of a system embodying this invention will be in part pointed out and in part apparent as the description thereof progresses. This invention relates to an improvement in certain features of the prior application of T. J. Judge, Ser. No. 613,353, filed May 25, 1932, which improvements will be claimed in the present application.

In describing the invention in detail, reference will be made to the accompanying drawings, in which those parts having similar features and functions are designated throughout the several views by like letter reference characters which are generally made distinctive either by reason of distinctive exponents representative of their location or by reason of preceding numerals representative of the order of their operation, and in which:-

Figs. 1 and 2, when placed end to end, illustrate the line circuits of a system embodying the present invention, which system includes a control office and a plurality of field stations;

Fig. 3 illustrates the apparatus employed at a typical field station arranged in accordance with the present invention;

Figs. 4, 5, and 6, when considered together as hereinafter explained, illustrate the apparatus and circuit arrangements employed at a typical control cffice and adapted to be associated with the apparatus employed at the field stations;

Fig. 7 illustrates an operation chart for indication; and,

Fig. 8 illustrates a typical code table.

For the purpose of simplifying the illustrations and facilitating in the explanation, the various parts and circuits constituting the embodiment of the invention have been shown diagrammatically and certain conventional illustrations have been employed, the drawings having been made more with the purpose in mind of making it easy to understand the principles and mode of operation, than with the idea of illustrating the specific construction and arrangement of parts that would be employed in practice. Thus, the various relays and their contacts are illustrated in a conventional manner, and symbols are used to indicate connections to the terminals of batteries, or other sources of electric current, instead of showing all of the wiring connections to these terminals.

The symbols and are employed to indicate the positive and negative terminals respectively of suitable batteries, or other sources of direct current; and the circuits with which these symbols are used, always have current flowing in the same direction. The symbols (B+) and. (3-) indicate connections to the opposite terminals of a suitable battery, or other direct current source which has a central or inter-- mediate tap designated (CN) with which these symbols are used, may have current flowing in one direction or the other depending upon the particular terminal used in combination with the intermediate tap (CN). When alternating current is used in place of direct current, the particular symbols employed represent the relative instantaneous polarities.

Communication system generally.- -The genand the circuits eral plan of organization of a system contemplated by the present invention may be best understood by placing Figs. 1 and 2 end to end, which illustrates the line circuits of a system having a control omce and two field stations. It is to be understood of course, that the system may be extended so as to provide as many field stations as necessary to govern the territory placed under the supervision of the operator in the control office, but for convenience in describing the present invention, only a first and a second field station have been shown in the present embodiment.

A control line wire It extends from the control oflice to the first field station, from the first field station to the second field station, and so on to the end of the system where it is connected to the control line return wire l2 which extends from the control oifice through each of the field stations. Similarly, an indication line wire M extends from the control oflice to the first field station, from the first field station to the second field station, and so on, to the end of the system where it is open ended. Associated with this indication line wire I4 is anindication line return wire l6 which extends from the control ofiice through the several field stations and to which the indication line is connected at that particular field station selected for the transmission of indications during a cycle of operation, as more specifically explained hereinafter. Although a four wire system has been shown for convenience in illustrating one embodiment of the present invention, it is to be understood that one common return wire may be used in place of the two return wires [2 and I6. In other words, the system may be termed a two line circuit system which circuits may be combined in any suitable manner, such as by the provision of a single common return, thereby making a three line Wire system, or by both line circuits superimposed upon two line wires by employing distinctive currents such as direct current and alternating current, or by the use of two frequencies which do not have common harmonics.

The control line circuit includes a three position biased-to-neutral polarized line relay F (with suitable exponent) at the control office and at each field station. Energy for the control line circuit is supplied from a control battery CB in the control office with the particular polarity selected by pole changing contacts located on code sending relays PC and NC. When the code sending relay PC is energized, a positive impulse is placed on the control line circuit, but when the code sending relay NC is energized, a negative impulse is placed upon the control line circuit. With both the code sending relays PC and NC energized or deenergized the control line circuit is maintained deenergized. Whenever energy is applied to the control line circuit by the code sending relays, such energization is broken up into time spaced impulses by the periodic operation of an impulsing contact of the relay EP.

The indication line circuit includes message relays in its two branches in the control office and includes pulsing contacts in the corresponding branches at each field station. As corresponding branches are selected at the control ofiice and at each field station when the control line circuit is energized closing front contacts on the repeating relays for the control line circuit, and as corresponding branches. are connected in series during the deenergized condition of the control line circuit as repeated at the control ofiice and at each field station by the closure of suitable back contacts, these two branches of the indication line circuit at the control office and at each field station may be conveniently termed front and back branches. In the control office, a message relay MB is included in the back branch, and similarly, a message relay MF is included in the front branch. At each field station, the front and back branches are respectively conditioned by pulsing relays PF and PB (with suitable exponents) in accordance with the code call and indications to be transmitted. The indication line circuit is supplied with energy from a suitable indication battery IB located in the control office.

Both line circuits are normally deenergized, but for the purpose of rendering the system capable of initiation by each field station, the connecting of the indication line wire at any field station to its return line wire results in the initiation of the system for the transmission of indications. v

Control ofiice equipment-The control ofiice (see Figs. 4, 5, and 6) includes a control machine having'a group of control levers for each field station, a miniature track layout corresponding in every way to the actual track layout in the field and various indicating lamps or equivalent devices together with apparatus and circuits to accomplish the desired functioning of the system.

That part of the control ofiice illustrated, shows more particularly that part of a control machine which is typical of the apparatus associated with a single field station having a track switch, a cross-over or the like, together with the general transmitting apparatus employed in common by all the field station units of the system.

Instead of showing the apparatus and circuit arrangements of the control office in an illustration of the aggregate divided between several sheets of drawings, the apparatus has been divided into three groups, with that apparatus which is commonv between the groups being illustrated fragmentarily in all groups except one, where its control circuits are illustrated in detail. In other words, the control circuits for each relay will be completely found on at least one sheet, but all of the circuits controlled by that relay may not be found on the same sheet of drawings.

With this explanation of the manner of disclosure of one embodiment of a control office for a system of the present invention, it may be stated that the apparatus for a single track switch comprises a switch machine control lever SML (see Fig. 5), a self-restoring starting button SB (with suitable preceding numeral), a miniature track switch ts, and a track occupancy indicating lamp OS (see Fig. 6). Similarly, a signal control lever (not shown) would also be associated therewith but for convenience has been omitted, as the control of a track switch may be considered as typical of the control of other types of trafiic controlling devices.

The movement of the switch machine control lever SML from one extreme position to the other followed by the actuation of its corresponding starting button ISB results in the normal or reverse operation of the track switch at the corresponding field station controlled through the medium of the communication system of the present invention.

Associated with each group of control levers is a change storing relay CH (with suitable preceding numeral) and a code determining relay CD (with suitable preceding numeral). Although only the control lever for a single field station has been illustrated, the starting buttons, ISB, 28B, andv 38B for several field stations have been illustrated together with their respective relays ICH, ZCH, and 3CH and their corresponding code determining relays ICD, 2CD, and 3CD.

The actuation of a starting button SB (with suitable preceding numeral) causes the energization of its corresponding change relay CH which in turn energizes the corresponding code determining relay for transmitting a code for the selection of the associated field station if the system is at rest. However, in the event that the system is in operation, the change relay-CH remains energized and causes the energization of its corresponding code determining relay CD the next time the system enters a condition of rest, provided of course, that no other more superior starting button has been actuated.

In the event that several starting buttons are actuated simultaneously or in rapid succession, the change relays CH and code determining relays CD together with a code determining stick relay CDS, are so interlocked that only one code determining relay may be picked up for any one particular cycle of operation with the interlock so arranged that the relays CD arepicked up in a predetermined sequence dependent upon their location in the bank relays.

Associated with each code determining relay CD is a corresponding group of code jumpers. Also, a cancelling button CNB is provided to cancel the operation of the starting buttons when so desired.

The control office includes, as previously mentioned a control line relay F of the three position biased-toneutral polarized type (see Fig. 4). This line relay F has associated therewith a neutral quick acting line repeating relay FP which repeats each energization and each deenergiza-' tion of the line relay F irrespective of the polarity with which the relay F is energized. For purposes later to be explained, the quick acting neutral relay FP is provided with a neutral quick acting repeating relay 2FP.

A slow acting line repeating relay SA is picked up at the beginning of each cycle of operation and is dropped at the end of each cycle of operation. This neutral slow acting relay SA has such slow acting characteristics that its pick-up time is relatively slow compared to the. pick-up time of the neutral relay FP, for example, but is relatively quick in picking up as compared with its drop-away period. The drop-away period of this relay SA is sufficiently retarded so that its contacts remain in picked up positions between successive impulses applied to the control line circuit during a cycle of operation, as repeated by the neutral relay 2FP. Also. the relay SA has associated therewith, a neutral slow acting repeating relay 28A having similar characteristics as the relay SA which is provided for purposes hereinafter pointed out.

Associated with the line relay F and its repeating relays, is a bank of stepping relays including relays IV, 2V, 3V and a last step relay LV together with a half-step relay VP. This bank of stepping relays is provided to mark off the steps of each cycle of operation.

An impulsing relay E is jointly controlled by the stepping relays and the half-step relay VP, which impulsing relay E together with a repeating relay EP governs the time spacing of the impulses on the control line circuit. Associated with the relay EP is a branch dividing relay DV which repeats the condition of the relay EP for the purpose of selecting the front and back branches of the indication line circuit in the control ofiice.

The polarity of the impulses applied to the control line circuit from the control battery CB, is determined by the code sending relays PC and NC, as previously mentioned. These relays are controlled in accordance with the position of those code jumpers and control levers which are rendered effective for a particular cycle of operation by the corresponding code determining relay CD.

As previously mentioned, the two neutral message receiving relays MB and MF are provided to repeat the condition of the indication line circuit for each step. The conditions of these relays are stored in suitable pilot relays and indication storing relays for registering that station having indications to transmit and for registering the indications transmitted (see Fig. 6).

For the purpose of illustrating the feature of station registration, the pilot relays IPB and 2PB are controlled on the first and second steps in accordance with the conditions received by the message receiving relay MB; while pilot relays IPF and 21F are controlled on the first and second steps in accordance with the conditions received by themessagereceiving relay MF. If a larger number of field stations are employed than may be registered by this pilot relay bank, more steps may be employed and additional pilot relays provided. These pilot relays are of the neutral type provided with stick circuits which maintain those relays energized, which are once picked up during a cycle, until the end of that cycle of operation. Following the positioning of the pilot relays, a station relay ST (with suitable numeral) is selected in accordance with the station registered.

It is well understood that with four two-position relays sixteen different selections may be made, thus fifteen station relays are provided, and the sixteenth combination is employed as the phantom station code call for purposes well understood in connection with a duplex system of the type contemplated by the present invention.

Following the registration of a station by the picking up of a station relay, suitable indication storing relays, such as relays IRF and IRB, for example, which are of the two-position polarized magnetic stick type, are positioned on the remaining steps of the cycle of operation for storing the indications transmitted from that field station which has been registered in.

For the purpose of initiating the system and determining whether such operation occurs at a field station or at the control office, the relays CI-IP, C, and F0 are provided. The functions of these relays will be more readily apparent from the description given hereinafter, it being suflicient for the present to know that the relay C is always picked up for a control cycle and the relay F0 is always picked up for an indication cycle.

The control o'fiice equipment also includes vari- "ous sources of current supply, bus wires and circuit connections, indicator lamps, overload protection and such other devices as may be needed for the proper functioning of such a system.

Field station equipment.The field station illustrated in Fig. 3 of the accompanying drawings is typical of all field stations of the system and may be adapted for use at the first, second, or any other location by merely altering certain code jumpers and selections to arrange for the proper code. But for convenience in the description, it is assumed that this field station is at the first location along the line circuits extending from the control office, and is so designated by reason of the distinctive exponents employed.

With reference to Fig. 3, a turn-out track is illustrated as connected to a main track by a track switch TS. This track switch TS is operated from one extreme locked position to the other by a suitable switch machine SM.

This switch machine SM is governed by a switch machine control relay SMR which is of the two-position polar magnetic stick type and which is governed from the control ofiice through the medium of the communication system herein disclosed. The relay SMR controls the operation of the switch machine SM by energizing its normal or reverse operating wires from a source local to the field station in any suitable wellknown manner, which control of course preferably includes suitable approach and detector looking so as to prevent the unsafe operation of the track switch TS.

Atlhough only the remote control of the switch machine SM has been indicated, it is to be understood that a dual control selector may be associated therewith for the purpose of local manual operation of the track switch TS.

Suitable signals are associated with the track switch TS for governing traific thereover and are provided with automatic block signalling means with selections made in accordance with the position of the track switch TS and condition. of the detector track section and such other sections of track and trafiic controlling devices as may be associated therewith.

These signals are also contemplated as governed from the control office through the medium of the communication system by positioning suitable control relays, which are governed similarly as the switch machine control relay SMR. All such control has been omitted for the sake of simplifying the present disclosure.

Associated with the signals governing traffic over the track switch TS is a suitable signal indicating relay M which is normally energized but is deenergized whenever any one of the signals is actuated or caused to'give a proceed indication.

A detector track section having a normally closed track circuit is provided with a track relay T and a suitable track battery for indicating the passage of trains over the track switch TS.

The communication part of the system includes at the field station a three position} biased-to-neutral polar line relay F, as previously mentioned, together with its quick acting line repeating relay FP These relays FF and SA have similar characteristics as the corresponding relays in the control oflice, the only difference being in the control of these relays which is subject to certain conditions explained in detail hereinafter.

The field station includes a bank of stepping relays lV, 2V, 3V, and LV together with a half step relay VP arranged in a similar manner as the stepping relay bank in the control office. However, the operation of the stepping relay bank at the field station is dependent upon station selection both during the transmission of controls and during the transmission of indications.

For the selection of the station for the reception of controls, a stationselecting outbound relay SO together with a stick relay SOS is provided to determine when the code call placed upon the control line circuit corresponds to the code call assigned to the field station.

The selection of a station for the transmission of indications is rendered available at the field station by the continued energization of the lockout relay LO. When the lock-out relay L is picked up for a cycle of operation, the pulsing relays PB and PF are effective to transmit the code call of the station followed by a transmission of the indications. I

A stick relay SB is provided to determine the restoration of the station in a positive manner at the end of each cycle ofoperation, as hereinafter explained.

A change relay CI-Pis provided to register a change in any of the trafiic controlling devices at the station, so that the system will be initiated for the transmission of new indications.

At each field station, suitable compensating resistance IE andZR are provided to compensate for the diiference in distance betweenthe field station at which they are located and the control office. In other words, the field station at the end of the system requires no resistances,

but for each station nearer the control oilice, higher resistances are employed so that the same current from the indication battery IB always flows through the indication line circuit irrespective of which particular station is transmitting. The resistance 2R is employed during the transmission'of indications; while the resistance IR is employed during the lock-out period at the beginning of a cycle of operation. The resistance IE is of a lower value than the resistance 2R as the lower winding of the lockout relay L0 is included in series therewith.

The field station also includes suitable bus wires, circuit connections, code jumpers, overload devices, and other devices and apparatus necessary for a centralized trafiic controlling system as contemplated in accordance with the present invention. 5

It is believed that the nature of the invention,

its advantages and characteristic features can be best understood with further description being set forth from the standpoint of operation.

Operation The system of the present invention is nor-- mally in a condition of rest, but may be initiated into a cycle of operation either from the control office or from any of the field stations whenever there are new controls or new indifor transmission at the same time, the indications are transmitted from such field stations to the control office, one station at a time on separate operating cycles.

It may happen, that there are new controls and new indications ready to be transmitted at the same time and in such instances controls are to be transmitted to a selected field station and simultaneously therewith indications are transmitted from that field station or some other field station during the same cycle of operation.

Although the embodiment of the present invention is capable of duplex transmission, that is, the simultaneous transmission of controls and indications, it is convenient to first consider the transmission of controls and indications separately and then point out the operation during a duplex cycle.

Normal at rest conditions.-Th e line circuits of the system are arranged to be normally deenergized, and similarly the remaining circuits of the system are arranged to be normally deenergized with a few exceptions.

For example, the detector track circuit associated with the track switch TS (see Fig. 3) is preferably of the closed circuit type, as previously mentioned. Also, the change relay CH is normally energized by a stick circuit closed from through a circuit including front contact 20 of the relay M, front contact 2| of track relay T, front contact 22 of change relay CH lower winding of change relay CH to Manual starting.-With the system in a condition of rest or a period of blank, it may be manually initiated into a cycle of operation for the transmission of controls to any desired station. Whenever such a cycle of operation is desired, the operator first positions the control levers of that particular station with which he desires to communicate and then actuates the corresponding starting button.

Although the operator may position the levers and actuate the starting buttons simultaneously or in rapid succession, suitable means is provided so that the code call of only one station is transmitted during'any one particular cycle of operation. This feature is provided by an interlocked relay bank in the control oflice associated with the control levers and starting buttons for the several stations. The sequence between control operations following the actuation of a large number of starting buttons is more conveniently discussed, after a description of the transmission of controls to a single field station has been given.

Let us assume that the operator desires to transmit controls to a field station, such as,

: ISB (see Fig. 5).

for example, the first field station (see Figs. 2 and 3). To do this, he first positions the control levers associated therewith, such as the control lever SML, and then actuates the starting button The actuation of the starting button closes a pick-up circuit for the change relay ICH from through a circuit including the back point of the starting button ISB, windings of the relay lCI-I, front point of the cancelling button CNB, to

As soon as the contacts of the relay ICH respend to such energization, a stick circuit is closed from through a circuit including back contact 23 of code determining relay ICD.

- front contact 24 of change relay ICH, windings of relay ICH. front point of the cancelling button CNB, to

The picking up of the contacts of the relay I CH also closes a pick-up circu t for 2h c g repeating relay CHP which is common to all of the change relays in the interlocked bank. This pick-up circuit is closed, providing the system is at rest, from through a circuit including back contact 25 of relay SA, back contact 26 of starting and cycle controlling relay FC, upper winding of the change repeating relay CHI, front contact 21 of the change relay ICH, to

The energization of the change repeating relay CHP is in turn repeated by the control office starting and cycle controlling relay C by reason of a circuit closed from through a circuit including back contact 28 of slow acting relay SA, front contact 29 of relay CHP, windings of relay C, to The picking up of the contacts of the relay CHP closes its stick circuit from through a circuit including back contact 30 of the last stepping relay LV, front contact 3| of relay CHP, lower Winding of the relay CHP, to Similarly, the relay C closes its stick circuit from through back contact 32 of relay ZSA, front contact 33 of relay C, windings of relay C, to

It is noted that the stick circuit for the relay CHP is closed. through the back contact 30 of the last stepping relay, and hence the relay CHP will remain energized throughout the cycle of operation, until the last step has been taken. Also, the relay C is temporarily stuck up through back contact 32 of relay ZSA which is opened as soon as the cycle is initiated, but the front contact 28 of relay SA is closed prior to the picking up of the contacts of the relay ZSA, so that the relay C is maintained energized during the cycle of operation. However, at the end of the cycle of operation, later to be pointed out, the relays SA and ZSA are deenergized successively, so that contact 28 of relay SA is opened before back contact 32 of relay ZSA is closed, thus allowing the relay C suificient time to drop away at the end of such cycle of operation.

The energization of the relay ICH also accom plishes the energization of its corresponding code determining relay ICD as soon as the control office starting and cycle controlling relay C is picked up, providing of course that the system is at rest, that there are no other code determining relays CD (with suitable preceding numerals) already picked up, and that there is no preceding change relay CH energized. This As soon as the contacts of the relay ICD have responded to such energization, a stick circuit is completedfrom through a circuit including front contact 63 of relay CHP in multiple with back contact 64 of relay EP, windings of relay CDS, front contact 65 of relay ICD, lower winding of relay ICD, front contact of cancelling button CNB, to

It is apparent that this stick circuit will be prepared by the front contact 63 of relay CHP prior to the picking up of the contacts of relay ICD, as it is necessary that the relay CHP be picked up to pick up the relay C before the relay ICD can respond. Thus, the back contact 64 of relay EP, included in multiple with front contact 63 of relay CHP, is unnecessary at the beginning of a cycle of operation, but-this combination of contacts is essential at the end of the cycle of operation so as to maintain the relay ICD energized until after the removal of the last impulse applied to the control line circuit, all of which will be pointed out hereinafter in connection with the end of the operating cycle. During the cycle, the relay CHP is maintained steadily energized through its stick circuit including back contact 30 of relay LV, so that the front contact 63 included in the stick circuit I CD is closed continuously during the cycle. However, the back contact 64 of relay EP is periodically opened and closed during the cycle, as the relay EP is the one which impulses the control line circuit.

The energization of the relay CDS, which is quick acting as compared to the relays CD (with suitable preceding numerals), opens its back contact 36 immediately upon its energization, thereby preventing thev energization of some other code determining relay. This function will be described more in detail under a consideration of the sequence of station selection for controls.

The energization of the relay ICD opens its back contact 23 and closes its front contact 23, thereby transferring the stick circuit of the relay ICH to the control of back contact 66 of relay 3V. In other Words, with the relay ICD picked up, a stick circuit for the relay ICH is closed from (-1-), through a circuit including back contact 66 of stepping relay 3V, front contact 23 of relay ICD, front contact 24 of relay ICH, windings of relay ICH, front contact of the cancelling button CNB, to It will be apparent that the contact 23 must be of the make-before-break type of contact in. order to insure that the relay ICH is not momentarily deenergized during this transfer of its stick circuit. It will also be understood in this connection that the back contact 55 is always on the stepping relay last in the bank and immediately preceding the last step relay LV.

From the above description, the manner in which the relays C and lCD are conditioned as a result of the manual actuation of the starting button 183 will be apparent, and such conditioning of these relays prepares the system for 'the transmission of a series of code impulses of selected polarities, as presently to be explained.

Polarity selection of stepping impulses. Whenever the system is initiated from the control office resulting in the energization of the starting relay C (see Fig. 5) and .the energization of a code determining relay, such as relay ICD, the impulses placed upon the line circuit for the succeeding cycle of operation are of polarities in accordance with the positions of the code jumpers and the control levers rendered effective by the picking up of that particular code determining relay.

As soon as the code determining relay ICD is picked up following the energization of the relay C, one or the other of the code sending relays PC and NC is energized depending on the position of the first code jumper.

More specifically, if the code jumper 40 is in a lower position, as illustrated, the relay PC is energized, but if the code jumper 40 is in an upper position the relay NC is energized. For example, assuming the code jumper 40 to be in a lower position, the relay PC is energized from through front contact 4| of the relay C,

back'contacts 42, 43 and 44 of relays 3V, 2V and iv respectively, code bus 45, front contact 46 of relay ICD, code jumper 40 in a lower position, positive bus 41, winding of the relay PC, to The energization of the relay PC results in the application of a positive impulse on the control line circuit, as will be more readily seen by considering the line circuits illustrated in Figs. 1 and 2. It apparent that with the code jumper 40in the opposite position, the negative bus 48 will-be energized, resulting in the energization of NC instead of relayPC.

Referring to'Figs. 1 and 2 and assuming, for example, that the relay PC is energized, the control line circuit is energized from the positive terminal of the control battery CB, through a circuit including back contact 50 of the negative code sending relay NC, front contact 5! of the positive code sending relay PC, back contact 52 of the impulsing repeating relay EP, windings of the line relay F, through the control line wire ill to the first field station, windings of the line relay F at the first field station, through the control line wire Ill to the second field station, windings of the line relay F at the second field station, and similarly through the remaining field stations to the control line return wire i2 at the last field station, and thence to the control office through the several field stations, front contact 53 of the positive code sending relay PC, back contact 54 of the negative code sending relay NC, to the negative terminal of the control battery CB.

This energization of the control line circuit is of course repeated by the three position biasedto-neutral polarized line rela-ysF (with suitable exponents) at the control office and at the several field stations by actuating their contacts to right hand positions. It is apparent that the energization of the relay NC instead of the relay PC reverses the direction of current flow in the control line circuit and causes the contacts of the relays F (with suitable exponents) to be actuated to left hand positions instead of right hand positions.

Assuming that the application of the first impulse to the control line circuit results in the subsequent deenergization of the control line circuit by the relay EP, and the picking up of the stepping relay IV, all in a manner hereinafter explained. it will be seen that one or the other of the code sending relays PC and NC will be energized depending upon the position of the code jumper 55.

For example, with the code jumper 55 in the position illustrated, the energization of the positive code sending relay PC is continued by a circuit from (I), through a circuit including front contact 4| of the relay C, back contacts 42 and 43 of the relays 3V and 2V respectively, front contact 44 of the relay IV, code bus 56, front contact 51 of the relay ICD, code jumper 55 in an upper position, positive bus 47, windings of the relay PC, to i t will be apparent, that with the code jumper 55 in a lower dotted line position, the negative code bus 48 will receive potential, thereby resulting in the energization of the relay NC instead of the relay PC.

Assuming that the application of the second impulse to the control line circuitresults in the subsequent deenergization of the control line circuit by the impulsing relay EP and in the picking up-of the stepping relay 2V, all in a manner hereinafter explained, it will be seen that one or the other of the code sending relays PCand NC will be energized depending upon the position of the code jumper 58.

For example, with the code jumper 58 in the position illustrated, the energization of the neg ative code sending relay NC is accomplished by a circuit closed from through a circuit including front contact 4| of relay C, back contact 42 of relay 3V, front contact 43 of relay 2V, code bus 59, front contact 60 of relay ICD, code jumper 58 in an upper position, negative bus 48, windings of relay NC, to

It will be apparent that with the code jumper 58 in its lower dotted line position, that the positive bus 41 will receive potential instead of the negative bus 48, thereby energizing the relay PC instead of the relay NC.

Assuming that the application of the third impulse to the control line circuit results in the subsequent deenergization of the control line circuit by the impulsing relay EP and also the picking up of the stepping relay 3V, all in a manner hereinafter explained, it will be seen that one or the other of the code sending relays PC and NC will be energized depending upon the position of the switch machine control lever SML.

For example, with the switch machine control lever in the position illustrated, the code sending relay NC is energized by a circuit closed from through a circuit including front contact 4| of relay C, front contact 42 of stepping relay 3V, code bus 6|, front contact 62 of relay ICD, switch machine control lever SML in a right hand position, negative code bus 48, windings of relay NC, to

It will be apparent that if the lever SML is in a left hand position instead of aright hand position, that the positive code bus 41 will receive potential instead of the negative code bus 48, thereby resulting in the energization of the positive code sending relay PC instead of the negative code sending relay NC.

From the above description it will be seen that the control line circuit is initially energized, as the relay EP is deenergized (see Figs. 1 and 4), upon the energization of one or the other of the code sending relays PC and NC following the energization of the cycle controlling relay C and the code determining relay- ICD. As presently to be explained, the application of the first impulse to the control line circuit results, after a predetermined time in the deenergization of the control line circuit by the picking up of the relay EP opening back contact 52. During such deenergization of the control line circuit, the next step is taken which transfers the energy supplied through front contact 4| of the relay C to the next code bus in succession, thereby selectively energizing one or the other of the code sending relays PC and NC so that upon the dropping of the relay EP and the closure of back contact 52, an impulse of selected polarity is applied to the control line circuit.

In other words, the operation of the stepping relays causes energy to be applied to the several code buses 45, 56, 59, and SI, in succession, and such energization is applied to the positive or negative code buses in accordance with the positions of the code jumpers and control levers selected by that particular code determining relay which is energized.

It should be particularly noted, that the operation of the step-by-step relays shifts the energization from one code bus to another during that time when the control line circuit is deenergized by the open condition of back contact 52 of relay EP (see Figs. 1 and 4), so that the change in position of the relays PC and NC is immaterial insofar as the then existing condition of the line circuit is concerned.

It is now considered expedient to explain how the impulses applied to the control line circuit operate the stepping relay bank followed by a description of how these impulses are suitably time spaced by the response of the stepping relay bank in the control oflice.

Operation of stepping relay bank.The control line circuit is initially energized at the beginning of a cycle of operation, as pointed out above. Such energization is terminated upon thepicking up of the back contact 52 of the relay EP (see Figs. 1 andv 4), during which time the code sending relays PC and NC are positioned for the application of the next impulse. In other words, time spaced impulses are placed upon the control line circuit by the periodic operation of the contact 52 of the relay EP; while the particular polarities of these impulses are determined by the contacts 50, 53, and 54 of the code sending relays PC and NC.

Assuming for the time being that time spaced impulses are suitably placed upon the control line circuit, each impulse being of a selected polarity, we may consider the step-by-step operation of the stepping relay bank.

Each impulse on the control line circuit is repeated by the polarized line relays F (with suitable exponents), but irrespective of the particular polarity of such impulse, the line repeating irelays FP (with suitable exponents) repeat each energization and each deenergization. For example, the actuation of polar contact 51 of relay F (see Figs. 1 and 4) to either of its positions connects positive energy to one terminal of the relay FP, while negative energy is permanently connected to the opposite terminal of this relay. The relay FF is sufficiently quick acting to respond to each energization and each deenergization of the relay F which completes an energizing circuit through front contact 68 for its repeater relay 2FP upon each energization.

The repeating relay 2FP is sufficiently quick acting to follow the relay FP, and completes an energizing circuit for the slow acting relay SA each time it is picked up by reason of the closure of its front contact 69.

Upon the application of the first impulse, which is repeated by the relay ZFP, the relay SA is energized through front contact 69 and after a time, determined by the slow acting characteristics of this relay, its contacts assume energized positions. This closes a circuit for its repeater relay 2SA through front contact 10, so that the contacts of the relay ZSA assume energized positions after a time period determined by its slow acting characteristics.

In brief, the relays F, FP, ZFP, SA, and A pick up in succession, each being a direct repeater of the next preceding relay. These successive relay operations serve to mark off the sequential stages in the initiation of the system at the beginning of each cycle, as well as serving to select the branches of the indication line circuit during each cycle of operation (explained hereinafter). For example, the picking up of the contacts of the relays FP (with suitable exponents) at the control office and at each field station marks the end of the initiation period at the beginning of a cycle; while the picking up of the contacts of the relays SA (with suitable exponents) at the control office and at each field station marks the end of the look-out period and the beginm'ng of the transmitting part of the cycle.

Forgetting for the time the various operations which occur during the starting of the system, and assuming that a predetermined time after the picking up of the relays SA; that the control line is deenergized followed by energizations and deenergizations alternately, we may consider the operation of the stepping relay banks. It is to be understood of course, that the relays F, FF and 2FP follow each condition of the control line circuit, while the relays SA and 2SA remain picked up throughout the cycle of operation, as they are provided with such slow acting characteristics that they are maintained picked up between successive applications of energy to the control line circuit.

As the stepping relay banks at the control oifice and at each field station are similar, the description will be directed more particularly to the control oifice stepping bank (see Fig. 4), and only the distinct differences between the control office stepping bank and a typical field station stepping bank will be pointed out in connection with the field station illustrated in Fig. 3.

With reference to Fig. 4, the picking up of the contacts of the relay SA upon the first impulse (first energized period) of a cycle with the con tacts of the relay ZFP already picked up, closes a pickup circuit for the relay VP from through a circuit including front contact II of relay SA, front contact I2 of relay ZFP, back contact I3'of relay IV, windings of relay VP, to As soon as the contacts of the relay VP have picked up, a stick circuit is closed from through a circuit including front contact II of relay SA, front contact 14 of relay VP, back contact I3 of relay IV, windings of relay VP, to

Upon the following deenergization of the control line circuit (first deenergized period) the relay 2FP is deenergized, thereby closing a pickup circuit for the relay IV from through a circuit including front contact I5 of relay SA, back contact I6 of relay EFP, front contact TI of relay VP, back contact I8 of relay 2V, windings of relay IV, to As soon as the contacts of the relay IV assume picked up positions, a stick circuit is closed from through a circuit including front contact I5 of relay SA, front contact I9 of relay IV, windings of relay IV, to Although the stick circuit for the relay VP including back contact I3 of stepping relay IV is opened when the relay IV is picked up, the relay VP is previously energized through its other stick circuit closed from through a circuit including front contact II of relay SA, back contact I2 of relay ZFP, front contact 8-!) of relay VP, windings of relay VP, to

Upon the following energization of the control line circuit (second energized period), as repeated by the relay ZFP, the relay VP is deenergized, as its stick circuit including front contact 86 is opened at back contact I2 of relay ZFP, and its stick circuit including its front contact I4 is opened at back contact I3 of relay IV.

The next deenergized condition of the control line circuit (second deenergized period), as repeated by the relay ZFP, causes the second stepping relay 2V to be energized through a pick-up circuit closed from through a circuit including front contact I5 of relay SA, back contact I8 of relay ZFP, back contact II of relay VP, back contact 8| of relay 3V, front contact 82 of relay IV, windings of relay 2V, to As soon as its contacts are picked up, a stick circuit is closed from through a circuit including front contact 75 of relay SA, front contact 83 of relay 2V, windings of relay 2V, to

The following energized condition of the control line circuit (third energized period), as repeated by the relay ZFP, closes a pick-up circuit for the relay VP from through a circuit including front contact. II of relay SA, front contact iii of relay ZFP, back contact 84 of relay 3V, front contact 35 of relay 2V, windings of relay VP, to The closure of front contact I4 of relay VP completes a stick circuit from through a circuit including front contact II of relay SA, front contact M of relay VP, back contact 84 of relay 3V, front contact 85 of relay 2V, windings of relay VP, to

The next deenergized condition of the control line circuit (third deenergized period), as repeated by the relay ZFP, causes the third stepping relay 3V to be energized through a pick-up circuit closed from through a circuit including front contact I5 of relay SA, back contact I6 of relay 2FP, front contact ll of relay VP, front contact 86 of relay 2V, windings of relay 3V, to As soon as the contacts of the relay 3V are picked up, a stick circuit is closed from through a circuit including front contact I5 of relay SA, front contact 81 of relay 3V, windings of relay 3V, to

Although the stick circuit for the relay VP including back contact 84 and front contact 14 is opened when relay 3V is picked up, its other stick circuit including front contact and back contact I2 is closed prior to the response of the relay 3V.

When the relay ZFP picks up in response to the next energized condition of the control line circuit (fourth energized period), the relay VP is deenergized, as its stick circuit including front contact 80 is opened at the back contact I2 of the relay ZFP, and as its stick circuit including front contact M is opened at back contact 84 of relay With the stepping relay 3V picked up, the deenergization of the relay VP upon the fourth energized period closes a pick-up circuit for the slow acting last step relay LV, from through a circuit including back contact 88 of relay VP,

front contact 89 of relay 3V, windings of relay LV, to As soon as the contacts of the relay LV are picked up, a stick circuit is closed from through a circuit including front contact 99 of relay 2SA, front contact 9| of relay LV, windings of relay LV, to Thus, the relay LV, when once picked up, is maintained energized until the system has returned to normal at rest conditions upon the deenergization of the relay 2SA at the end of the operating cycle.

It should also be noted in this connection, that if the stepping relay bank included an even number of stepping relays instead of the odd number, as illustrated, the relay VP would be in an energized position when the last stepping relay LV is picked up upon the fourth energization of the control line circuit, so that it would be necessary for the back contact 88 of relay VP to be replaced by a front contact.

As the fourth impulse on the control line circuit is the last in a cycle of operation for the present embodiment, the next deenergization of the control line circuit (fourth deenergized period) continues until the system returns to normal conditions of rest and is again initiated. At the end of the cycle when the relay SA drops its contacts a predetermined time after the beginning of such fourth deenergized period, the stick circuits for the stepping relays are opened at front contact and all the stepping relays assume deenergized positions at substantially the same time.

Also, the opening of front contact H of relay SA at the end of a cycle of operation, would deenergize the relay VP if this relay VP were in a picked up position, which would be the case if a stepping relay bank having an even number of stepping relays were employed.

It should be understood, that these circuit connections for a stepping relay bank may be extended for as many steps as may be required for a system in actual practice, but for the purpose of illustrating the present invention only three stepping relays have been employed together with a last step relay LV, for purposes hereinafter explained.

The stepping relay banks at each of the field stations (see Fig. 3 for example) are substantially identical in operation, as the stepping relay bank already explained, with the exception that the stepping operation is made dependent upon certain station selections, as hereinafter pointed out in connection with the description of the station selection.

Impulsing of control line circuitlhe initial application of the first impulse to the control line circuit results in the successive energization of the relays F, FP, 2FP, SA, and VP. The energization of the relay SA is of course followed by the picking up of the contacts of the relay 2SA, which completes a pick-up circuit for the relay E prepared by the picking up of the contacts of the relay VP. This pick-up circuit is closed from through a circuit including front contact 90 of relay ZSA, front contact 92 of relay VP, back contact 93 of relay IV, bus wire 94, upper winding of relay E, to This energization of the relay E isrepeated by the relay EP by reason of the closure of front contact 95.

Upon the picking up of the contact 52 of the relay EP, the control line circuit is deenergized which is repeated by the relays F, FF, and 2FP, but the relay SA is sufficiently slow acting to maintain its contacts in picked up positions until the succeeding application of energy to the control line circuit.

The deenergization of the relay 2FP causes the first stepping relay EV to be picked up, as previously explained, and this opens the energizing circuit of the relay E at back contact 93 thereby allowing its contact 95 to open and deenergize the relay EP. This deenergization of the relay EP closes the back contact 52 included in the control line circuit causing the next impulse (second energized period) to be applied to the control line circuit in accordance with the position of the relays PC and NC, as set up during the time in which the relay EP is energized and the contact 52 is opened.

This energization of the control line circuit (second energized period) is repeated by the relays F, PP and 2FP, and as soon as the relay 2FP is picked up, the relay VP is deenergized.

This completes a pick-up circuit for the relay E from through a circuit including front contact 90 of relay 2SA, back contact 92 of relay VP, back contact 95 of relay 2V, front contact 91 of relay IV, bus wire 98, lower winding of relay E, to This energization of relay E is repeated by the relay EP and again results in the deenergization of the control line circuit (second deenergized period).

This second deenergization of the control line circuit is repeated by the relays F, PP, and 2FP, but the relay SA is sufiiciently slow acting to maintain its contacts in picked up positions until the next succeeding application of energy to the control line circuit. The deenergization of the relay 2FP causes the second stepping relay 2V to be picked up, as previously explained, and this opens the energizing circuit of the relay E at back contact 95, thereby allowing contact 95 of the relay E to open and deenergize the relay EP. This deenergization of the relay EP closes its back contact 52 included in the control line circuit causing the next impulse (third energized period) to be applied to the control line circuit in accordance with the positions of the relays PC and NC as set up during the time in which the relay EP is energized and the contact 52 is opened.

This energization of the control line circuit (third energized period) is repeated by the relays F, FP and 2FP, and as soon as the relay 2FP is picked up, the relay VP is energized. This completes a pick-up circuit for the relay E from through a circuit including front contact 90 of relay ZSA, front contact 92 of relay VP, back contact :83 of stepping relay 3V, front contact lil l of stepping relay 2V, bus wire 94, upper winding of the relay E, to This energization of the relay E is repeated by the relay EP and again results in the deenergization of the control line circuit (third deenergized period).

This third deenergization or" the control line circuit is repeated by the relays F, FF, and 2FP,

but the relay SA is sufficiently slow acting to maintain its contacts in picked up positions until the succeeding application of energy to the control line circuit. The deenergization of the relay ZFP causes the stepping relay 3V to be picked up, as previously explained, and this opens the energizing circuit of the relay E at back contact E03, thereby allowing its contact 95 to open and deenergize the relay EP. This deenergization of the relay EP closes the back contact 52 included in the control line circuit causing the next impulse (fourth energized period) to be applied to the control line circuit in accordance with the positions of the relays PC and NC, as set up during the time which the relay PC is energized and the contact 52 is opened.

This energization of the control line circuit (fourth energized period) is repeated by the relays F, FF, and REP, and as soon as the relay 2FP is picked up, the relay VP is deenergized.

cycle of the present embodiment of the invention, means is provided to prolong such-deenergized condition of the control line circuit until the relays SA and 2SA assume deenergized positions, and even then the deenergized condition of the control line circuit is continued unless another cycle of operation is initiated.

As previously pointed out the last step relay LV is picked up as soon as the relay VP responds to the fourth deenergization of the control line circuit, so that in addition to the energizing circuit for the relay E including front contact I of relay 3V another energizing circuit is completed through front contact I06 of relay LV, which circuit is maintained until the relay ZSA has dropped away opening front contact 90. This energizing circuit for the relay E at the end of a cycle of operation is closed from through a circuit including front contact 9!] of relay ZSA, back contact 92 of relay VP, front contact I96 of relay LV, bus wire 94, upper winding of the relay E, to

The particular operations which occur at the end of a cycle of operation will be described more particularly under a corresponding heading.

The impulsing operation may be summarized by stating that the relays F, FP, 2FP, VP, E, EP and the relays of the stepping relay bank continue during the operation of the system in what may be termed cycles of operation, irrespective of the number of steps, until the last impulse has been placed upon the control line circuit, after which the control line circuit is maintained opened by the last step relay LV to cause the system to enter a period of rest.

In brief, the initial period of the energization of the control line circuit includes the pick-up periods of the relays F, FP, 2FP, SA, ESA, E, and EP; while the succeeding periods of energization include the pick-up periods of the relays F, FP, ZFP, VP, E, and EP. Then the deenergized periods between successive impulses applied tothe control line circuit include the drop-away periods of the relays F, FP, and ZFP, the pick-up period of a stepping relay and the drop-away periods of the relays E and EP.

Station selection for cont1'0ls.-The manner in which a predetermined number of impulses of selected polarities are applied to the control line circuit to comprise a cycle of operation has been explained in detail. The positive and negative characters of these impulses are arranged in accordance with the particular code jumpers and control levers which are effective for that cycle of operation.

It will be apparent from the line circuit illustrated in Figs. 1 and 2, that these impulses are received at all of the field stations, and are repeated by the line relay F (with suitable exponent) at each station, but for convenience in describing the operation of the field stations, reference will be more particularly made to Fig. 3 which illustrates a typical station in detail and which for convenience is considered to be the first field station in the system.

The application of the first impulse to the control line circuit causes the line relay F to actuate its polar contacts to either right or left hand positions dependent upon the positive or negative character of the impulse. However, the actuation of polar contact IM to either a right hand or a left hand position causes the application of energy to the pick-up circuit for the relay FP This pick-up circuit for relay FP is closed from through a circuit including polar contact llll of relay F in either a right or a left hand position, back contact I02 of relay SE windings of relay FP to This energization of the relay FP closes the energizing circuit for the relay SA from through a circuit including front contact 591 of relay FP winding of relay SA to After a time marked off by the slow acting characteristics of the relay SA its contacts pick up thereby closing a pick-up circuit for the relay SE from through a-circuit including front contact I08 of relay SA windings of relay SB to From this it is apparent that the relays F F1 SA and SB pick up in succession. Similan successive operations of the corresponding relays occur at all of'the field stationsi In other words, the relays FP (with suitable exponents) at the several field stations are all insured of being picked up by reason of a pick-up circuit including a back contact of their corresponding relays SB (with suitable exponents). However, the relays FP (with suitable expoments) are maintained energized throughout the remainder of the first impulse following the picking up of the relays SB (with suitable exponents) and are maintained operable throughout the remainder of the cycle, only at those stations still having possibilities of selection by reason of the picked up condition of the relays- S0 (with suitable exponents) at such stations.

If the first impulse of the code call placed upon the control line circuit is of one character, a part of the field stations will have their selecting relays SO picked up during the application of the first impulse; while if the first impulse of the code call placed upon the control line circuit is of the other character, the remaining field stations will have their selecting relays SO picked up during the application of the first SO drop out. Thus, at only one station of the system Will the relay FP (with suitable exponent) operate throughout the control cycle of operation, as those relays SO which'are picked up at the beginning of a cycle are selectively dropped out until only one remains (presentlyto be explained).

For example, assuming relay S0 to be picked up (see Fig. 3), a controlling circuit for the relay FP is closed from through a circuit including polar contact Iill of relay F in either 1 a right or a left hand position, back contact Hi9 of relay L0 front contact ll!) of relay S0 windings of relay FP to v At those field stations where the relays S0 (with suitable exponents) do not pick up, there is an energizing circuit which is closed for the relays. SA (with suitable exponents) even prior to the picking up of the relays FP (with suitable exponents). For example, assuming that the relay SO (see Fig. 3) does not pick up at the beginning of a cycle, then as soon as the relay F is energized, there is a circuit for the relay SA closed from through a circuit including polar contact [0| of relay F 'in either a right i or a left hand position, back contact I09 of relay LO, back contact H0 of relay SO, windings of relay SA to In other words, at this station when the relay S0 is not picked up at the beginning of a cycle, the relay SA is energized prior to the picking up of the relay FP, but as the relay SA is considerably slower acting than the relay FP the relays F, FP and SA pick up in succession, as previously stated. This earlier response of the relay SA is immaterial insofar as the operation is concerned, but is pointed out merely for the sake of completeness.

Also, at those stations where the relays S0 (with suitable exponents) are picked up at the beginning of the cycle, the energizing circuits for the relays SA (with suitable exponents) which include the back contacts of the look-out relays and the selecting relays, such for example as back contacts H19 and H0 (see Fig. 3), are closed until the relays S0 (with suitable exponents) respond. If the relays S0 (with suitable exponents) pick up simultaneously with the relays FP (with suitable exponents), then the relays SA (with suitable exponents) are continuously energized subsequent to the response of the relays F (with suitable exponents). In this case, the relays F, FP and SA (with suitable exponents) pick up in succession, as pointed out above, by reason of the fact that relays SA (with suitable exponents) are slow acting as compared to the relays F? (with suitable exponents).

On the other hand, the relays S0 (with suitable exponents) may respond more quickly to their energization than the relays FP (with suitable exponents), so that the energization of the relays SA (with suitable exponents) is but temporary until their respective relays FP (with suitable exponents) are picked up. In such cases, the relays SA (with suitable exponents) may be considered as being effectively energized only subsequent to the picking up of the relays FP (with suitable exponents). In such cases, the relays F, FF, and SA (with suitable exponents) pick up sequentially, as will be readily apparent. These various combinations of timing operations which occur during a control cycle are immaterial insofar as the control cycle of operation is concerned, but are pointed out for the sake of completeness.

We may now consider the manner in which the relays S0 (with suitable exponents) may be selectively picked up at the beginning of a cycle of operation and selectively dropped out during such a cycle until only one remains energized at the end of the station selecting steps. As illustrative of the way in which positive and negative impulses may be combined to form a number of distinctive code calls for several field stations, there is shown a typical code table in Fig. 8 where eight different combinations or code calls may be obtained by three successive impulses for the selection of stations to receive control impulses. In this type of code, a choice of a positive or a negative impulse on each of three steps gives eight different combinations. Similarly, four impulses on each of four steps gives sixteen different code calls, and the same method of arrangement of code calls may be carried on for any number of additional impulses, each additional impulse doubling the number of possible distinctive code calls.

Upon referring to the code table shown in Fig. 8, it will be noted that in this type of code arrangement, the character of the impulse on the control line circuit for the first energized period is positive for one-half the total number of code calls and negative for the other half, so that a selection is made between half of the total number of stations on the first impulse depending upon whether it is a positive or a negative impulse. Similarly, the impulse on the second energized period of the control line circuit is positive for one-half of the code calls remaining after the first selection, and negative for the other half, so that a selection is made between half of those stations selected by the first impulse, thereby leaving only one-quarter of the total number of stations. The impulse on the third energized period selects in a similar manner depending upon its character between those stations selected by the first two impulses, thereby carrying the selection to oneeighth of the total number. In other words, on the first impulse, half of the total number of stations may be selected and the other half discarded with the process of subdividing continuing until the desired individual station is the only one whichremains.

For reasons explained hereinafter, the eighth code call is assigned to a phantom station, so that with three station selecting impulses, only seven actual stations may be employed.

For convenience in describing this station selecting feature of the present invention, reference will be made more particularly to Fig. 3 of the accompanying drawings which illustrates the relays and circuits employed at a typical field station. This typical field station has its code jumpers Ill, H2, and H3 so arranged, as to make this station responsive to a code call comprising three impulses of This arrangement corresponds with the character of the impulses transmitted over the control line circuit when the code jumpers 40, 55 and 58 are rendered effective by the code determining relay [CD in the control oifice (see Fig. 5) to govern the impulses placed upon the control line circuit. This code call is the station selecting code No. 2 illustrated in the typical code table of Fi 8.

As intimated above, the station selecting relays S0; (with suitable exponents) are selectively picked up at the beginning of a cycle of operation. If the character of the first impulse is positive then the relays SO are selectively picked up at one-half of the field stations and are left de-energized at the other half; while if the first impulse of the cycle is negative in character the situation will be reversed. Then on the second impulse, one-half of those station selecting relays SO which have been picked up during the first impulse are selecaively dropped out depending upon the correspondence between the character of the impulse and the code jumpers at the respective stations. Similarly, ion the third impulse, one-half of those SO relays still remaining from the first and second impulses are dropped out, and this selection is carried on until only one station selecting relay SO remains energized. More specifically, if the character of the first impulse applied to the control line circuit for a control cycle is positive then the relays SO and SOS (see Fig. 3) will be picked up upon such impulse, as will similarly the remaining field stations of the system which have code calls beginning with a positive impulse. For example, this pick-up circuit for the relays SOS and S0 is closed upon the response of the relay F vfrom through a circuit including 

